Pure Brew New Scientist 21 Mar 98
THE world's first caffeine-free coffee plants will be planted this summer in a greenhouse in Hawaii. If all goes to plan, beans from the plants will not need to be decaffeinated chemically in processes which can damage beans and spoil their flavour. "I'm expecting my first sip of decaffeinated coffee from them in around 20 months,' says John Stiles, who developed the beans at the University of Hawaii in Manoa. Stiles, who last week attended a meeting of the International Scientific Association of Coffee in Paris, says the altered plants are growing as tissue cultures in the laboratory. 'We expect to plant them in the greenhouse in three months'time," he says. Stiles and his colleagues had earlier identified the master gene that governs caffeine production. The gene makes xanthosine-N7-methyl transferase, the enzyme that kick-starts caffeine production. To silence the gene, Stiles used a bacterium, Agrobacterium tumefaciens, to shuttle an antisense gene into embryonic tissue. Antisense genes are back-to-front versions of a target gene, and block its function. Stiles attached the antisense gene to genetic switches that would make it active throughout the coffee plant. Sure enough, the plants produced just 3 per cent of the normal amount of caffeine. Stiles says the gene had to be silenced throughout the plant because in earlier studies, he found the coffee beans didn't produce much of the enzyme. He suspects that early stages of caffeine production take place elsewhere, possibly in the leaves, ordy later concentrating in the beans. Some wild species of coffee contain no caffeine. But Stiles is the first to make a virtually caffeine-free variety of a commercial species--Coffea arabica. This accounts for 60 per cent of all coffee consumed. Coffee is normally decaffeinated by treating the beans either with hot water or with supercritical carbon dioxide. "They can damage the beans, and are not completely specific for caffeine, eliminating some flavour compounds too," says Stiles. He now hopes to develop caffeine-free tea, as the same gene controls caffeine production in tea. Andy Coghan
Engineering biodegradable plastic lawns Apr 98
A team of scientists at an English university is close to perfecting the cash crop of the 21st century - plastic which grows in the ground. Beef farmers driven to ruin by mad-cow disease may soon be harvesting paddocks of the raw material to make biodegradable cling-film, bottles and medical sutures. The five-man team of biochemists and genetic engineers at Durham University has taken a gene from a bacterium found in soil and inserted it into the DNA of rape, a plant commonly cultivated for its oil which is used in cooking and, to make margarine. That gene makes a protein which makes a polymer - the building block of all plastics which is environmentally friendly to make and will rot away in the backyard compost heap. 'You start with no chemicals the team's leader, Dr Yieran Elborough, told the NewZealand Herald, "just sunlight, soil and water. "Then you throw it into the compost and it turns into carbon dioxide and water." The conventional method of plastic manufacture uses non- renewable crude oil.